Z Axis reversal

Need help troubleshooting hardware issues... talk here

Z Axis reversal

Postby JamesHind » 2016-Nov-Mon-12-Nov

Hi, I've been printing on my new Printrbot simple metal for months, I've made dozens of different objects with no calibration issues. I use Cura, version 15.04.5 I had to move the machine from one room at work to another and since then I've had problems. I've searched the forum for similar problems but not found any that match.

The Printer seems to level the bed fine at the start of the print but the first layer often doesn't deposit. After that it starts grinding into the bed. I think that the Z axis is reversed somehow. What I'm struggling with is that the initial levelling seems OK (If I use the bed levelling wizard in Cura's 'expert' settings then the command 'Down 10mm' raises the head printer head away from the bed, as it always has done). Only when it prints an object does it seem to reverse.

I'm wondering if the initial bed levelling (where it homes and puts some drops of PLA down) is controlled differently to when it is printing objects and if this means that a problem in the Gcode is more or less likely to be causing the issues than a mechanical issue. To confound my troubleshooting, I also had a student use it unsupervised on the day of the move! I'd be grateful for any advice the forum could provide.
  • 0

JamesHind
Waiting to connect to printer...
 
Posts: 4
Joined: 2016-Nov-Mon-11-Nov
Reputation: 0

Z Axis reversal

Sponsor

Sponsor
 

Re: Z Axis reversal

Postby RetireeJay » 2016-Nov-Mon-12-Nov

Ask your student what he did. Maybe he "solved the problem" of the printer going up when you tell it to go down. In reality, I don't see how it could have been working before, but as they say "if it ain't broke, don't fix it."
  • 0

Printrbot Plus operational January 2013
Brass threaded rods (5/16" X 18) & nuts for Z axis
GT2 belts & pulleys
Cable chain to reduce probability of fatigue failure in wires
E3D V5 Hot End, 0.4mm nozzle, also 0.8 and 0.25 in use occasionally
PB fan mount + 40mm fan -- using printed mount adapter, not the E3D supplied fan
Injection molded extruder gears
Optical Z "endstop" (custom designed and built)
Have used many pounds of T-Glase filament. Now also doing some work with Ninjaflex SemiFlex
Print on glass with Scotch Craft Stick or other glue stick
User avatar
RetireeJay
My next printer is...
 
Posts: 4776
Joined: 2013-Jan-Wed-13-Jan
Location: Greenville, SC
Reputation: 477

Re: Z Axis reversal

Postby JamesHind » 2016-Nov-Tue-03-Nov

Now I'm even more confused. I thought the 'Down' command in the levelling wizard was supposed to move the printrbot head up (on account of Cura being made for ultimakers, where the bed is what moves on the Z axis)?
  • 0

JamesHind
Waiting to connect to printer...
 
Posts: 4
Joined: 2016-Nov-Mon-11-Nov
Reputation: 0

Re: Z Axis reversal

Postby RetireeJay » 2016-Nov-Tue-07-Nov

In my copy of Cura, I have specified "Printrbot Plus..." under the "Machine" tab. My printer's head moves up (away from the bed) when I click on an "up" icon on the printer control screen.
  • 0

Printrbot Plus operational January 2013
Brass threaded rods (5/16" X 18) & nuts for Z axis
GT2 belts & pulleys
Cable chain to reduce probability of fatigue failure in wires
E3D V5 Hot End, 0.4mm nozzle, also 0.8 and 0.25 in use occasionally
PB fan mount + 40mm fan -- using printed mount adapter, not the E3D supplied fan
Injection molded extruder gears
Optical Z "endstop" (custom designed and built)
Have used many pounds of T-Glase filament. Now also doing some work with Ninjaflex SemiFlex
Print on glass with Scotch Craft Stick or other glue stick
User avatar
RetireeJay
My next printer is...
 
Posts: 4776
Joined: 2013-Jan-Wed-13-Jan
Location: Greenville, SC
Reputation: 477

Re: Z Axis reversal

Postby Mooselake » 2016-Nov-Tue-08-Nov

Up means more room between the print platform and hot end, moving whatever the printer requires (head down, bed up, teleportation, more gas in the balloon, etc) to attain that goal. The slicer neither knows or cares how it happens, just that it does

Kirk
  • 0

Modified KickStarter Classic Plus 7/2012
KS Thingybot Delta Pro 10/31/16
User avatar
Mooselake
My next printer is...
 
Posts: 3507
Joined: 2011-Dec-Tue-23-Dec
Location: Moose Swamp, Upper Michigan, USA
Reputation: 170

Re: Z Axis reversal

Postby JamesHind » 2016-Dec-Thu-02-Dec

Then I do have problems! Could either of you point to an online guide for Z axis problems? I'm not great with electronics but I need it working again and I have no expert on hand to fix it.
  • 0

JamesHind
Waiting to connect to printer...
 
Posts: 4
Joined: 2016-Nov-Mon-11-Nov
Reputation: 0

Re: Z Axis reversal

Postby RetireeJay » 2016-Dec-Thu-07-Dec

JamesHind wrote:Could either of you point to an online guide for Z axis problems? I'm not great with electronics but I need it working again and I have no expert on hand to fix it.

It's very simple. If you tell your User Interface to move the extruder Up and it instead moves Down, then simply unplug the Z motor connector from the Printrboard, turn it end-for-end, and plug it back in again. That will reverse the direction of the motor.

There's a picture of the Printrboard with the Z motor connector (and others) posted here.

When you try to unplug the connector, don't just tug on the wires; try to pull on the connector body. You may find that there is a kind of latch that has snapped into place and keeps the connector from coming off. If that's the case, use a screwdriver to lever the white tab coming up from the board away from the connector on the end of the cable; that will release the latch. It may be that when you plug it back in in the reverse orientation you will notice that there's no latching action; that's OK, don't worry about it.

There are plenty of posts in the forum about taming the Z axis. There are really only two things that need attention if things are working properly: Calibration, meaning steps per mm in Z, and Zeroing. The Calibration has been standardized for a couple of years now, based on the thread specification on the threaded rod, so you don't have to think about it at all. Zeroing means getting the nozzle height just right above the bed for printing the first layer. On printers with the probe, like yours, that mostly involves getting a software offset number dialed in correctly - and that procedure is documented in Printrbot's own pages.
  • 1

Printrbot Plus operational January 2013
Brass threaded rods (5/16" X 18) & nuts for Z axis
GT2 belts & pulleys
Cable chain to reduce probability of fatigue failure in wires
E3D V5 Hot End, 0.4mm nozzle, also 0.8 and 0.25 in use occasionally
PB fan mount + 40mm fan -- using printed mount adapter, not the E3D supplied fan
Injection molded extruder gears
Optical Z "endstop" (custom designed and built)
Have used many pounds of T-Glase filament. Now also doing some work with Ninjaflex SemiFlex
Print on glass with Scotch Craft Stick or other glue stick
User avatar
RetireeJay
My next printer is...
 
Posts: 4776
Joined: 2013-Jan-Wed-13-Jan
Location: Greenville, SC
Reputation: 477

Re: Z Axis reversal

Postby JamesHind » 2016-Dec-Fri-09-Dec

Thanks for this - I've been able to reverse the motor - unfortunately now, rather than going down until it finds the bed, when it starts up it goes up and up and up! As I said before, the behaviour of the Z axis is opposite when it begins levelling the bed (where the laser sensor stops it) and when printing. Your advice for reversing the motor was very useful - now I just need to look into whatever else is wrong with the start up bit!
  • 0

JamesHind
Waiting to connect to printer...
 
Posts: 4
Joined: 2016-Nov-Mon-11-Nov
Reputation: 0

Re: Z Axis reversal

Postby RetireeJay » 2016-Dec-Fri-09-Dec

JamesHind wrote:unfortunately now, rather than going down until it finds the bed, when it starts up it goes up and up and up! As I said before, the behaviour of the Z axis is opposite when it begins levelling the bed (where the laser sensor stops it) and when printing.

That's very strange. We've seen problems like that with the Y axis because some versions of Printrbot printers "home" to Y = 0 whereas others "home" to Y = Max, and if the firmware installed on the board doesn't match the actual hardware switch location then things get confused. But I've never before heard of "homing" in Z in the wrong direction!

It seems like this must be a "settings" problem somewhere. It might help to take a close look at all your settings, both in Cura and in EEPROM.
In Cura, of course your Machine should be a Printrbot (discussed previously in this thread). In addition to that, take a look at your startup code (in the "Start/End-Gcode" tab) to see if there's anything going on with Z.
Here's my Cura startup code. Any line that starts with a semicolon is "commented out" and not executed, so only five lines are actually active. Note that my personal preference is to do homing manually before I start a print, and I don't have a probe so I never use G29. Therefore your startup code will be different, but this might help you to compare with a "known good" version.
Code: Select all
;Sliced at: {day} {date} {time}
;Basic settings: Layer height: {layer_height} Walls: {wall_thickness} Fill: {fill_density}
;Print time: {print_time}
;Filament used: {filament_amount}m {filament_weight}g
;Filament cost: {filament_cost}
;M190 S{print_bed_temperature} ;Uncomment to add your own bed temperature line
;M109 S{print_temperature} ;Uncomment to add your own temperature line
G21        ;metric values
G90        ;absolute positioning
M82        ;set extruder to absolute mode
;M107       ;start with the fan off
;G28 X0 Y0  ;move X/Y to min endstops
;G28 Z0     ;move Z to min endstops
;G1 Z15.0 F{travel_speed} ;move the platform down 15mm
G92 E0                  ;zero the extruded length
;G1 F200 E3              ;extrude 3mm of feed stock
;G92 E0                  ;zero the extruded length again
G1 F{travel_speed}
;Put printing message on LCD screen
;M117 Printing...


And here are the "generic" EEPROM settings provided by Printrbot for a Rev F board. Note that their build volume matches the largest machine they make; your values in the M211 line will be smaller.
Code: Select all
M503
Steps per unit:
  M92 X80.00 Y80.00 Z2020.00 E96.00
Maximum feedrates (mm/s):
  M203 X125.00 Y125.00 Z5.00 E14.00
Maximum Acceleration (mm/s2):
  M201 X2000 Y2000 Z30 E10000
Acceleration: S=acceleration, T=retract acceleration
  M204 S3000.00 T3000.00
Advanced variables: S=Min feedrate (mm/s), T=Min travel feedrate (mm/s), B=minimum segment time (ms), X=maximum XY jerk (mm/s), 

Z=maximum Z jerk (mm/s),  E=maximum E jerk (mm/s)
  M205 S0.00 T0.00 B20000 X20.00 Z0.40 E5.00
Home offset (mm):
  M206 X0.00 Y0.00 Z0.00
PID settings:
   M301 P22.20 I1.08 D114.00
Min position (mm):
  M210 X0.00 Y0.00 Z0.00
Max position (mm):
  M211 X250.00 Y250.00 Z254.00
Bed probe offset (mm):
  M212 X20.00 Y0.00 Z0.00
  • 0

Printrbot Plus operational January 2013
Brass threaded rods (5/16" X 18) & nuts for Z axis
GT2 belts & pulleys
Cable chain to reduce probability of fatigue failure in wires
E3D V5 Hot End, 0.4mm nozzle, also 0.8 and 0.25 in use occasionally
PB fan mount + 40mm fan -- using printed mount adapter, not the E3D supplied fan
Injection molded extruder gears
Optical Z "endstop" (custom designed and built)
Have used many pounds of T-Glase filament. Now also doing some work with Ninjaflex SemiFlex
Print on glass with Scotch Craft Stick or other glue stick
User avatar
RetireeJay
My next printer is...
 
Posts: 4776
Joined: 2013-Jan-Wed-13-Jan
Location: Greenville, SC
Reputation: 477


Return to Troubleshooting talk

Who is online

Users browsing this forum: No registered users and 1 guest

cron